Jackson框架
一、Jackson簡介
Jackson可以輕鬆的將Java對象轉換成json對象和xml文檔，同樣也可以將json、xml轉換成Java對象。相比json-lib框架，Jackson所依賴的jar包較少，簡單易用並且性能也要相對高些。
二、Jackson使用
2.1、ObjectMapper的使用
建立兩個類Address、Employee
public class Address {
private String street;
private String city;
private int zipCode;
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public int getZipCode() {
return zipCode;
}
public void setZipcode(int zipcode) {
this.zipCode = zipcode;
}
@Override
public String toString(){
return getStreet() + ", "+getCity()+", "+getZipCode();
}
}public class Employee {
private int id;
private String name;
private int age;
private BigDecimal salary;
private String designation;
private Address address;
private long[] phoneNumbers;
private Map<String, String> personalInformation;
/*Getter and Setter Methods*/
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public BigDecimal getSalary() {
return salary;
}
public void setSalary(BigDecimal salary) {
this.salary = salary;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public long[] getPhoneNumbers() {
return phoneNumbers;
}
public void setPhoneNumbers(long[] phoneNumbers) {
this.phoneNumbers = phoneNumbers;
}
public Map<String, String> getPersonalInformation() {
return personalInformation;
}
public void setPersonalInformation(Map<String, String> personalInformation) {
this.personalInformation = personalInformation;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("ID: " + getId() + "\n");
sb.append("Name: " + getName() + "\n");
sb.append("Age: " + getAge() + "\n");
sb.append("Salary: $" + getSalary() + "\n");
sb.append("Designation: " + getDesignation() + "\n");
sb.append("Phone Numbers: " + Arrays.toString(getPhoneNumbers()) + "\n");
sb.append("Address: " + getAddress() + "\n");
sb.append("Personal Information:" + getPersonalInformation() + "\n");
return sb.toString();
}
}json格式的文件data.json如下：
{
"id" : 123,
"name" : "Henry Smith",
"age" : 28,
"salary" : 2000,
"designation" : "Programmer",
"address" : {
"street" : "Park Avn.",
"city" : "Westchester",
"zipcode" : 10583
},
"phoneNumbers" : [ 654321, 222333 ],
"personalInformation" : {
"gender" : "Male",
"maritialstatus" : "Married"
}
}1、從文件中讀取json或向文件中寫入json
//Jackson讀取json文件，將json數據轉化爲對象
public void testJsonToObject() throws JsonParseException, JsonMappingException, IOException{
ObjectMapper objectMapper = new ObjectMapper();
Employee emp = objectMapper.readValue(new File("src/data.json"), Employee.class);
System.out.println(emp.toString());
}
//Jackson將java對象轉化爲json字符串並輸出
public void testObjectTojson() throws JsonParseException, JsonMappingException, IOException{
ObjectMapper objectMapper = new ObjectMapper();
Employee emp = objectMapper.readValue(new File("src/data.json"), Employee.class);
//將對象轉化爲json格式，並存入到文件中
objectMapper.writeValue(new File("src/data1.json"), emp);
//將對象轉化爲json格式數據，並輸出到控制檯上
objectMapper.writeValue(System.out, emp);
// StringWriter str =new StringWriter();
// JsonGenerator s=new JsonFactory().createGenerator(str);
// objectMapper.writeValue(s, emp);
// String data =new String();
// str.write(data);
// System.out.println(data);
}2、從InputStream讀入或向OutPutStream寫出
public void testInputStream() throws JsonParseException, JsonMappingException, IOException{
ObjectMapper objectMapper = new ObjectMapper();
Employee emp = objectMapper.readValue(new FileInputStream("src/data.json"), Employee.class);
System.out.println(emp.toString());
}
public void testOutPutStream() throws JsonParseException, JsonMappingException, IOException{
ObjectMapper objectMapper = new ObjectMapper();
Employee emp = objectMapper.readValue(new File("src/data.json"), Employee.class);
//將對象轉化爲json格式，並存入到文件中
objectMapper.writeValue(new FileOutputStream("src/data1.json"), emp);
//JsonNode node = mapper.readTree(new File("country2.json"));
//將對象轉化爲json格式數據，並輸出到控制檯上
objectMapper.writeValue(System.out, emp);
}3、從URL中讀取數據（若URL返回的滿足Employee類的json數據）
Employee emp1 = objectMapper.readValue("http://www.xxx.com/xxx", Employee.class);
JsonNode jsonNode = objectMapper.readTree("http://www.xxx.com/xxx");
4、常用的方法
//將user對象轉化爲json格式字符串
String json=mapper.writeValueAsString(user)
//將json格式的字符串轉化爲對象，示例如下：
Map m = mapper.readValue(json, Map.class)
Employee emp = objectMapper.readValue(new File("src/data.json"), Employee.class);
public void testJsonGenerator() throws IOException{
URL url =new URL("http://www.xxx.com/xxx");
URLConnection urlConnection = url.openConnection();
urlConnection.setDoOutput(true);
urlConnection.setDoInput(true);
//產生一個JsonGenerator類
JsonFactory jsonFactory = new JsonFactory();
JsonGenerator jsonGenerator = jsonFactory.createGenerator(urlConnection.getOutputStream(), JsonEncoding.UTF8);
jsonGenerator.writeString("wwwwwwwww");
jsonGenerator.writeStartObject();
jsonGenerator.writeStringField("brand", "Mercedes");
jsonGenerator.writeNumberField("doors", 5);
jsonGenerator.writeEndObject();
jsonGenerator.close();
}